Comparative study of modified/non-modified aluminum and silica aerogels for anionic dye adsorption performance

Developing effective and low-cost adsorbents is of great significance for controlling water contamination. To eliminate anionic water contaminants, four modified/non-modified aluminum (Al_HMD, Al_OSSD) and silica (Si_HMD, Si_OSSD) aerogels have been successfully employed. The four as-prepared aerogels were applied as adsorbents for removal of an anionic dye (acid orange 7, AO) from aqueous solution. Compared to silica aerogels, aluminum aerogels showed efficient adsorption performance for anionic water contaminants. The AO maximum adsorption capacity of Al₂O₃ aerogel is twice as high as that of SiO₂ aerogel. The maximum adsorption capacity of aerogels was in the following order: Al_HMD > Al_OSSD > Si_HMD > Si_OSSD. Adsorption kinetics and isotherms of AO dye on the four as-prepared aerogels have also been studied. The kinetic data fitted well with the pseudo first-order kinetics model and the adsorption isotherm could be described by the Langmuir model. Adsorption rate of AO dye was mainly governed by film diffusion and intra-particle diffusion. Based on the adsorption mechanism, this work provides an idea for the design of superior adsorbents for anionic water contaminants.